The present invention relates to a polyolefin wax having a high melting point, reduced isotacticity, reduced crystallinity and reduced hardness and also to a process for its preparation.
The preparation of polyolefin waxes having a broad molecular weight distribution Mw/Mn and an isotactic index of from 60 to 80% by means of supported catalyst, cocatalyst and stereoregulator at temperatures of above 95xc2x0 C. is known (cf. DE-A 31 48 229). However, in addition to the high temperature, large amounts of hydrogen have to be used as molecular weight regulator. To achieve degrees of polymerization typical of waxes, the hydrogen partial pressure exceeds the partial pressure of the olefin. However, such polymerization conditions cause a significant olefin loss by hydrogenation to the alkane and decreased catalyst activities which result in high residual ash contents in the products. In particular, the high chlorine and titanium contents require complicated purification steps for the product.
The preparation of 1-olefin polymer waxes having a narrow molecular weight distribution and high isotacticity using metallocene catalysts (EP 321 852) is known. For many wax applications, the high isotacticity and hardness of these, products, which shows up in a high heat of fusion of more than 80 [J/g] for polypropylene waxes, is disadvantageous.
The preparation of a 1-olefin stereoblock polymer wax (EP 321 853) using metallocene catalysts which lower the isotacticity by means of a large number of misinsertions is known. Disadvantages are the low activity of these catalyst systems and the lack of controllability of the isotacticity.
The preparation of polyolefin waxes having different isotacticity by changing the polymerization temperature (EP 416 566 is known. However, disadvantages are that the activity of the catalyst decreases sharply with the polymerization temperature and that the achievable molecular weights are low and cannot be adjusted independently of the isotacticity.
Furthermore, it is known that the crystallinity can be reduced by copolymerization (EP 384 264). A disadvantage is the lowering of the melting point of the copolymers in comparison with the melting point of the homopolymer, which limits the range of applications.
It is therefore an object of the present invention to provide a polyolefin wax which avoids the disadvantages of the prior art and, in particular, has reduced isotacticity and hardness at the same time as high melting point.
The present invention accordingly provides a polyolefin wax having a melt viscosity of from 0.1 to 100,000 mPas, preferably from 1 to 60,000 mPas, particularly preferably from 50 to 60,000 mPas, at 170xc2x0 C., a DSC heat of fusion less than 80 J/g, a DSC melting point of greater than 130xc2x0 C. and a molecular weight distribution Mw/Mn of less than or equal to 3. Preference is given to polypropylene waxes.
The polyolefin waxes of the present invention can be extracted to an extent of at least 10% by weight with diethyl ether. A possible way of determining the isotacticity of crystalline polyolefin waxes is the extraction method using a solvent in a Soxhlet extractor, with the highly crystalline isotactic products remaining undissolved in the residue. The ether-extracted part corresponds to the atactic parts of the polyolefin wax.
The present invention also provides a process for preparing polyolefin waxes having a melt viscosity of from 50 to 100,000 mPas at 170xc2x0 C., a DSC heat of fusion less than 80 J/g, a DSC melting point of greater than 130xc2x0 C. and a molecular weight distribution Mw/Mn of less than or equal to 3, in the presence of a catalyst comprising a stereo-rigid metallocene compound A and a cocatalyst B. with the metallocene compound A being used as a mixture of racemic form and meso form in a rac/meso ratio of  less than 0.5.
In the racemic form (rac form) of the stereorigid metallocene compound A, the two enantiomers can be converted into one another only by the mirroring operation. In the case of the meso form, the structure and its mirror image can be converted into one another by rotation. The term meso form also includes the case where, when the ligands of the metallocene are different such as in dimethylsilyl(2-methylindenyl)(indenyl)ZrCl2, a second pair of enantiomers arises in which the more voluminous parts of the two ligand systems each lie above one another.
The compounds (b) and (c) below are accordingly the rac form and the compounds (a) and (d) below are the meso form. 
X=R7, ML2=M1R10R11 as defined for formula I
The stereorigid metallocene compound A is preferably a metallocene of the formula I 
where
M1 is titanium, zirconium, hafnium, vanadium, niobium or tantalum,
R1, R2, R31, R4 and R5 are identical or different and are each hydrogen, (C1-C20)alkyl, (C6-C14)aryl, (C1-C10)alkoxy, (C2-C10)alkenyl, (C7-C20)arylalkyl, (C7-C20)alkylaryl, (C6-C10)aryloxy, (C1-C10)fluoroalkyl, (C6-C10)haloaryl, (C2-C10)alkynyl, a radical xe2x80x94SiR63, where R6 is (C1-C10)-alkyl, a halogen atom or a heteroaromatic radical having 5 or 6 ring atoms and able to contain one or more hetero atoms, or adjacent radicals R1 to R4 together with the atoms connecting them form one or more rings,
R7 is a radical 
where
M2 is carbon, silicon, germanium or tin,
R8 and R8 are identical or different and are each hydrogen, (C1-C20)alkyl, (C6-C14)aryl, (C1-C10)alkoxy, (C2-C10)alkenyl, (C7-C20)arylalkyl, (C7-C20)alkylaryl, (C6-C10)aryloxy, (C1-C10)fluoroalkyl, (C6-C10)haloaryl, (C2-C10)alkynyl or halogen, or R8 and R9 together with the atom connecting them form a ring, p is 0, 1, 2 or 3 and R10 and R11 are identical or different and are each hydrogen, (C1-C10)alkyl, (C1-C10)alkoxy, (C6-C10)aryl, (C6-C10)aryloxy, (C2-C10)alkenyl, (C7-C40)arylalkyl, (C7-C40) alkylaryl, (C8-C40) arylalkenyl, hydroxy or a halogen atom.
The compound of the formula I is preferably one in which M1 is zirconium or hafnium, in particular zirconium, R1, R2, R31, R4 are identical or different and are each hydrogen, (C1-C10)alkyl, (C6-C14)aryl, (C1-C4)alkoxy, (C2-C6)alkenyl, (C1-C6)fluoroalkyl, a halogen atom or a heterocyclic aromatic radical having 5 or 6 ring atoms and able to contain one or more hetero atoms, or adjacent radicals R1 to R4 together with the atoms connecting them form a ring, and R5 is (C1-C10)alkyl,
M2 is carbon or silicon, in particular silicon, R8 and R9 are identical or different and are each hydrogen, (C1-C6)alkyl, (C6-C10)aryl, (C1-C6)alkoxy, (C2-C4)alkenyl, (C7-C10) arylalkyl, (C7-C10) alkylaryl, or R8 and R9 together with the atom connecting them form a ring, p is 1 or 2, preferably 1, and R10 and R11 are identical or different and are each hydrogen, (C1-C3)alkyl, in particular methyl, (C1-C3)alkoxy, (C6-C8)aryl, (C6-C8)aryloxy, (C2-C4)alkenyl, (C7-C10) arylalkyl, (C7-C10) alkylaryl, (C8-C12)arylalkenyl or a halogen atom, preferably chlorine.
Examples of the metallocene component of the catalyst system of the present invention are the rac and meso forms of the following metallocene compounds:
dimethylsilanediylbis(indenyl)zirconium dichloride dimethylsilanediylbis(tetrahydroindenyl)zirconium dichloride
dimethylsilanediylbis(4-naphthylindenyl)zirconium dichloride
dimethylsilanediylbis(2-methylbenzoindenyl)zirconium dichloride
dimethylsilanediylbis(2-methylindenyl)zirconium dichloride
dimethylsilanediylbis(2-methyltetrahydroindenyl)zirconium dichloride
dimethylsilanediylbis(2-methyl-4-(1-naphthyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-methyl-4-(2-naphthyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-methyl-4-phenylindenyl)zirconium dichloride
dimethylsilanediylbis (2-methyl-4-t-butylindenyl)zirconium dichloride
dimethylsilanediylbis(2-methyl-4-isopropylindenyl)zirconium dichloride
dimethylsilanediylbis(2-methyl-4-ethylindenyl)zirconium dichloride
dimethylsilanediylbis(2-methyl-4-xcex1-acenaphthindenyl)zirconium dichloride
dimethylsilanediylbis(2,4-dimethylindenyl)zirconium dichloride
dimethylsilanediylbis(2-ethylindenyl)zirconium dichloride
dimethylsilanediylbis(2-ethyl-4-ethylindenyl)zirconium dichloride
dimethylsilanediylbis(2-ethyl-4-phenylindenyl)zirconium dichloride
dimethylsilanediylbis(2-methyl-4,5-benzoindenyl)zirconium dichloride
dimethylsilanediylbis(2-methyl-4,6-diisopropylindenyl)zirconium dichloride
dimethylsilanediylbis(2-methyl-4,5-diisopropylindenyl)zirconium dichloride
dimethylsilanediylbis(2,4,6-trimethylindenyl)zirconium dichloride
dimethylsilanediylbis(2,5,6-trimethylindenyl)zirconium dichloride
dimethylsilanediylbis(2,4,7-trimethylindenyl)zirconium dichloride
dimethylsilanediylbis(2-methyl-5-isobutylindenyl)zirconium dichloride
dimethylsilanediylbis(2-methyl-5-t-butylindenyl)zirconium dichloride
methyl(phenyl)silanediylbis(2-methyl-4-phenylindenyl)zirconium dichloride
methyl(phenyl)silanediylbis(2-methyl-4,6-diisopropyl-indenyl)zirconium dichloride
methyl(phenyl)silanediylbis(2-methyl-4-isopropylindenyl)zirconium dichloride
methyl(phenyl)silanediylbis(2-methyl-4,5-benzoindenyl)zirconium dichloride
methyl(phenyl)silanediylbis(2-methyl-4,5-(methylbenzo)-indenyl)zirconium dichloride
methyl(phenyl)silanediylbis(2-methyl-4,5-(tetramethyl-benzo)indenyl)zirconium dichloride
methyl(phenyl)silanediylbis(2-methyl-4-xcex1-acenaphth-indenyl)zirconium dichloride
methyl(phenyl)silanediylbis(2-methylindenyl)zirconium dichloride
methyl(phenyl)silanediylbis(2-methyl-5-isobutylindenyl)zirconium dichloride
1,2-ethanediylbis(2-methyl-4-phenylindenyl)zirconium dichloride
1,2-ethanediylbis(2-methyltetrahydroindenyl)zirconium dichloride
1,2-ethanediylbis(tetrahydroindenyl)zirconium dichloride
1,4-butanediylbis(2-methyl-4-phenylindenyl)zirconium dichloride
1,2-ethanediylbis(2-methyl-4,6-diisopropylindenyl)zirconium dichloride
1,4-butanediylbis(2-methyl-4-isopropylindenyl)zirconium dichloride
1,4-butanediylbis(2-methyl-4,5-benzoindenyl)zirconium dichloride
1,2-ethanediylbis(2-methyl-4,5-benzoindenyl)zirconium dichloride
1,2-ethanediylbis(2,4,7-trimethylindenyl)zirconium dichloride
1,2-ethanediylbis(2-methylindenyl)zirconium dichloride
1,4-butanediylbis(2-methylindenyl)zirconium dichloride
and also the dialkyl derivatives of the abovementioned metallocenes, for example:
dimethylsilanediylbis(indenyl)dimethylzirconium
dimethylsilanediylbis(tetrahydroindenyl)diethylzirconium
dimethylsilanediylbis(2-methylbenzoindenyl)dimethylzirconium
dimethylsilanediylbis(2-methylindenyl)dibutylzirconium
and also the monoalkyl derivatives of the abovementioned metallocenes, for example:
dimethylsilanediylbis(indenyl)methylzirconium chloride
dimethylsilanediylbis(tetrahydroindenyl)ethylzirconium chloride
dimethylsilanediylbis(2-methylbenzoindenyl)methylzirconium chloride
dimethylsilanediylbis(2-methylindenyl)butylzirconium chloride.
Particular preference is given to the rac and meso forms of the following metallocene compounds:
dimethylsilanediylbis(2-methyl-4-xcex1-acenaphthindenyl)zirconium dichloride
dimethylsilanediylbis(2-ethyl-4-phenylindenyl)zirconium dichloride.
Particularly suitable compounds are the rac and meso forms of the following metallocene compounds:
dimethylsilyl(2-methyl-4,5-benzoindenyl)2ZrCl2 
dimethylsilyl(2-methylindenyl)2ZrCl2 
dimethylsilyl(2-methylindenyl) (2-methyl-4,5-benzo-indenyl)ZrCl2 
dimethylsilyl(2-methyl-4-phenylindenyl)2ZrCl2 
dimethylsilyl(2-methylindenyl) (2-methyl-4-phenylindenyl)2ZrCl2 
dimethylsilyl(2-methyl-4,6-diisopropylindenyl)2ZrCl2 
dimethylsilyl(2,5,6-trimethylindenyl)2ZrCl2 
dimethylsilyl(2-methyl-4-naphthylindenyl)2ZrCl2.
In the synthesis of the metallocene compound A used in the process of the present invention, the ratio of rac to meso form directly after the metallocene synthesis is generally between 2:1 and 0.5:1. However, crystallization allows the metallocene to be enriched in the desired form and the ratio of rac and meso forms to be set as desired.
A further possible way of adjusting the rac/meso ratio is the addition of an enriched, for example, meso form of a metallocene to a rac/meso 1/1 mixture from the synthesis. The enriched meso form of metallocenes is formed in large amounts in the preparation of the rac metallocenes for the preparation of highly isotactic polyolefin molding compositions.
In principle, the cocatalyst B in the process of the present invention can be any compound which, owing to its Lewis acidity, can convert the neutral metallocene into a cation and stabilize this (xe2x80x9clabile coordinationxe2x80x9d). In addition, the cocatalyst or the anion formed therefrom should undergo no further reactions with the metallocene cation formed (EP 427 697). The cocatalyst used is preferably an aluminum compound and/or a boron compound.
The boron compound preferably has the formula R12xNH4xe2x88x92xBR134, R12xPH4xe2x88x92xBR134, R123CBR134 or BR133, where x is a number from 1 to 4, preferably 3, the radicals R12 are identical or different, preferably identical, and are each C1-C10-alkyl or C6-C18-aryl, or two radicals R12 together with the atoms connecting them form a ring, and the radicals R13 are identical or different, preferably identical, and are each C6-C18-aryl which can be substituted by alkyl, haloalkyl or fluorine. In particular, R12 is ethyl, propyl, butyl or phenyl and R13 is phenyl, pentafluorophenyl, 3,5-bistrifluoromethylphenyl, mesityl, xylyl or tolyl (EP 277 003, EP 277 004 and EP 426 638).
The cocatalyst used is preferably an aluminum compound such as aluminoxane and/or an aluminum alkyl.
The cocatalyst used is particularly preferably an aluminoxane, in particular of the formula IIa for the linear type and/or the formula IIb for the cyclic type, 
where, in the formulae IIa and IIb, the radicals R14 are identical or different and are each hydrogen or a C1-C20-hydrocarbon group such as a C1-C18-alkyl group, a C6-C18-aryl group or benzyl, and p is an integer from 2 to 50, preferably from 10 to 35.
The radicals R1 are preferably identical and are each hydrogen, methyl, isobutyl, phenyl or benzyl, particularly preferably methyl.
If the radicals R14 are different, they are preferably methyl and hydrogen or alternatively methyl and isobutyl, with hydrogen or isobutyl preferably being present in a numerical proportion of from 0.01 to 40% (of the radicals R14).
The methods of preparing the aluminoxanes are known (DE 4 004 477).
The exact spatial structure of the aluminoxanes is not known (J. Am. Chem. Soc. (1993) 115, 4971). For example, it is conceivable that chains and rings join to form larger two-dimensional or three-dimensional structures.
Regardless of the manner of preparation, all aluminoxane solutions have in common a variable content of unreacted aluminum starting compound which is present in free form or as adduct.
It is possible to preactivate the metallocene compound of the present invention prior to use in the polymerization reactor using a cocatalyst, in particular an aluminoxane. This significantly increases the polymerization activity. The preactivation of the metallocene compound is preferably carried out in solution. Here, the metallocene compound is preferably dissolved in a solution of the aluminoxane in an inert hydrocarbon. Suitable inert hydrocarbons are aliphatic or aromatic hydrocarbons. Preference is given to using toluene.
The concentration of the aluminoxane in the solution is in the range from about 1% by weight to the saturation limit, preferably from 5 to 30% by weight, in each case based on the total amount of solution. The metallocene can be used in the same concentration, but it is preferably used in an amount of 10xe2x88x924-1 mol per mol of aluminoxane. The preactivation time is from 5 minutes to 60 hours, preferably from 5 to 60 minutes. The preactivation is carried out at a temperature of from xe2x88x9278 to 100xc2x0 C., preferably from 0 to 70xc2x0 C. The metallocene compound compound is here preferably used in a concentration, based on the transition metal, of from 10xe2x88x923 to 10xe2x88x928, preferably from 10xe2x88x924 to 10xe2x88x927 mol of transition metal per dm3 of solvent or per dm3 of reactor volume. The aluminoxane is preferably used in a concentration of from 10xe2x88x926 to 10xe2x88x921 mol, preferably from 10xe2x88x925 to 10xe2x88x922 mol, per dm3 of solvent or per dm3 of reactor volume. The other cocatalysts mentioned are used in approximately equimolar amounts to the metallocene compound. However, higher concentrations are also possible in principle.
In the process of the present invention, the metallocene compound is preferably reacted with the cocatalyst outside the polymerization reactor in a separate step using a suitable solvent. The catalyst can be applied to a support during this procedure.
In the process of the present invention, a prepolymerization can be carried out by means of the metallocene compound. For the prepolymerization, the (or one of the) olefin(s) used in the polymerization is preferably used.
The stereorigid metallocene compound A is preferably reacted with the cocatalyst B outside the polymerization reactor in a separate step using a suitable solvent. The catalyst can be applied to a support during this procedure. For this purpose, the metallocene compound can be first reacted with the support and subsequently with the cocatalyst. The cocatalyst can also be supported first and subsequently reacted with the metallocene compound. It is also possible to support the reaction product of metallocene compound and cocatalyst. During these processes of application to a support, the ratio of rac to meso form of the metallocene remains unchanged because of the similar chemical properties. Suitable support materials are, for example, silica gels, aluminum oxides or other inorganic supports such as magnesium chloride or graphite. The preparation of a supported cocatalyst can be carried out, for example, as described in EP 567952. Another suitable support material is a polymer powder as described, for example, in EP 563917.
The catalyst can be added as solution, as suspension or dry in supported form. Suitable solvents or suspension media for catalyst or cocatalyst are hydrocarbons generally such as toluene, heptane, hexane, pentane, butane or propane and also industrial diesel oils.
The polyolefin wax of the present invention is, owing to the broad adjustability of the hardness, suitable for a wide range of applications, e.g. as formulation component in toners in the case of high hardness, or as base for pigment preparation, as auxiliary in the processing of plastics and as melt adhesive (hot-melt) in the case of products of low hardness.
This process enables the preparation of polyolefin waxes having a narrow molecular weight distribution of less than 3. If the atactic part is enriched by ether extraction of the total sample, the GPC spectrum of the low-isotacticity part extractable with ether is virtually identical with the GPC of the total sample.
The process of the present invention can be carried out in solution, in suspension or in the gas phase at temperatures of from 40 to 120xc2x0 C., at an olefin partial pressure of from 1 to 50 bar, at a hydrogen partial pressure of from 0 to 10 bar, with addition (based on Al) of from 0.01 to 10 mmol of cocatalyst/liter of suspension medium at a catalyst/cocatalyst ratio of from 1:1 to 1:1000.
In the process of the present invention, preference is given to polymerizing olefins of the formula RaCHxe2x95x90CHRb, where Ra and Rb are identical or different and are each a hydrogen atom or an alkyl radical having from 1 to 28 carbon atoms, or Ra and Rb together with the carbon atoms connecting them form one or more rings. Examples of such olefins are propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, norbornene or norbornadiene. Preference is given to propylene.
In the polymerization, prior to the addition of the catalyst, a further organoaluminum compound C such as trimethylaluminum, triethylaluminum, triisobutylaluminum or isoprenylaluminum can be additionally added in a concentration of from 1 to 0.001 mmol of Al per dm3 of reactor volume for making the polymerization system inert.
The polymerization can be carried out batchwise or continuously and in one or more stages, with the low time-dependent decrease in the polymerization activity enabling any desired residence times to be realized.
The molecular weight of the waxes of the present invention can be regulated using hydrogen in accordance with the desired melt viscosity. This enables melt viscosities of PP waxes in the range from 50 to 100,000 mPas, measured at 170xc2x0 C., to be obtained. The molecular weight can also be regulated by changing the polymerization temperature.
The polyolefin waxes of the present invention are particularly suitable as additives, e.g. for plastics.